From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: "Eric W. Biederman" <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Jann Horn <jannh@google.com>,
Vasiliy Kulikov <segoon@openwall.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Oleg Nesterov <oleg@redhat.com>,
Christopher Yeoh <cyeoh@au1.ibm.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Sargun Dhillon <sargun@sargun.me>,
Christian Brauner <christian.brauner@ubuntu.com>,
Arnd Bergmann <arnd@arndb.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Waiman Long <longman@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH 3/3] exec: Transform exec_update_mutex into a rw_semaphore
Date: Fri, 4 Dec 2020 17:08:01 +0100 [thread overview]
Message-ID: <AM6PR03MB5170412C2B0318C40CED55E5E4F10@AM6PR03MB5170.eurprd03.prod.outlook.com> (raw)
In-Reply-To: <87ft4mbqen.fsf@x220.int.ebiederm.org>
Hi Eric,
I think I remembered from a previous discussion about this topic,
that it was unclear if the rw_semaphores are working the same
in RT-Linux. Will this fix work in RT as well?
On 12/3/20 9:12 PM, Eric W. Biederman wrote:
> --- a/kernel/kcmp.c
> +++ b/kernel/kcmp.c
> @@ -70,25 +70,25 @@ get_file_raw_ptr(struct task_struct *task, unsigned int idx)
> return file;
> }
>
> -static void kcmp_unlock(struct mutex *m1, struct mutex *m2)
> +static void kcmp_unlock(struct rw_semaphore *l1, struct rw_semaphore *l2)
> {
> - if (likely(m2 != m1))
> - mutex_unlock(m2);
> - mutex_unlock(m1);
> + if (likely(l2 != l1))
is this still necessary ?
> + up_read(l2);
> + up_read(l1);
> }
>
> -static int kcmp_lock(struct mutex *m1, struct mutex *m2)
> +static int kcmp_lock(struct rw_semaphore *l1, struct rw_semaphore *l2)
> {
> int err;
>
> - if (m2 > m1)
> - swap(m1, m2);
> + if (l2 > l1)
> + swap(l1, l2);
and this is probably also no longer necessary?
>
> - err = mutex_lock_killable(m1);
> - if (!err && likely(m1 != m2)) {
> - err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING);
> + err = down_read_killable(l1);
> + if (!err && likely(l1 != l2)) {
and this can now be unconditionally, right?
> + err = down_read_killable_nested(l2, SINGLE_DEPTH_NESTING);
> if (err)
> - mutex_unlock(m1);
> + up_read(l1);
> }
>
> return err;
> @@ -156,8 +156,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
> /*
> * One should have enough rights to inspect task details.
> */
> - ret = kcmp_lock(&task1->signal->exec_update_mutex,
> - &task2->signal->exec_update_mutex);
> + ret = kcmp_lock(&task1->signal->exec_update_lock,
> + &task2->signal->exec_update_lock);
> if (ret)
> goto err;
> if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
> @@ -212,8 +212,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
> }
>
> err_unlock:
> - kcmp_unlock(&task1->signal->exec_update_mutex,
> - &task2->signal->exec_update_mutex);
> + kcmp_unlock(&task1->signal->exec_update_lock,
> + &task2->signal->exec_update_lock);
> err:
> put_task_struct(task1);
> put_task_struct(task2);
Thanks
Bernd.
next prev parent reply other threads:[~2020-12-04 16:09 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 20:09 [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore Eric W. Biederman
2020-12-03 20:10 ` [PATCH 1/3] rwsem: Implement down_read_killable_nested Eric W. Biederman
2020-12-04 1:58 ` Waiman Long
2020-12-09 18:38 ` [tip: locking/core] " tip-bot2 for Eric W. Biederman
2020-12-03 20:11 ` [PATCH 2/3] rwsem: Implement down_read_interruptible Eric W. Biederman
2020-12-04 1:59 ` Waiman Long
2020-12-07 9:02 ` Peter Zijlstra
2020-12-07 15:33 ` Waiman Long
2020-12-07 16:58 ` David Laight
2020-12-07 19:02 ` Waiman Long
2020-12-08 9:12 ` David Laight
2020-12-08 12:32 ` Peter Zijlstra
2020-12-08 13:13 ` David Laight
2020-12-08 15:34 ` Waiman Long
2020-12-08 16:23 ` David Laight
2020-12-07 15:56 ` Eric W. Biederman
2020-12-08 14:52 ` Peter Zijlstra
2020-12-08 18:27 ` Eric W. Biederman
2020-12-09 18:36 ` Peter Zijlstra
2020-12-10 19:33 ` Eric W. Biederman
2020-12-11 8:16 ` Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] locking/rwsem: Introduce rwsem_write_trylock() tip-bot2 for Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] locking/rwsem: Fold __down_{read,write}*() tip-bot2 for Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] locking/rwsem: Better collate rwsem_read_trylock() tip-bot2 for Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] rwsem: Implement down_read_interruptible tip-bot2 for Eric W. Biederman
2020-12-03 20:12 ` [PATCH 3/3] exec: Transform exec_update_mutex into a rw_semaphore Eric W. Biederman
2020-12-04 16:08 ` Bernd Edlinger [this message]
2020-12-04 17:21 ` Linus Torvalds
2020-12-04 19:34 ` Eric W. Biederman
2020-12-04 20:10 ` Linus Torvalds
2020-12-04 20:30 ` Bernd Edlinger
2020-12-04 20:48 ` Linus Torvalds
2020-12-04 21:48 ` Davidlohr Bueso
2020-12-05 18:05 ` Eric W. Biederman
2020-12-07 9:15 ` Peter Zijlstra
2020-12-07 9:09 ` Peter Zijlstra
2020-12-07 18:40 ` Linus Torvalds
2020-12-08 8:34 ` [PATCH] perf: Break deadlock involving exec_update_mutex Peter Zijlstra
2020-12-08 18:37 ` Linus Torvalds
2020-12-10 18:38 ` Davidlohr Bueso
2020-12-10 19:40 ` Eric W. Biederman
2020-12-05 17:43 ` [PATCH 3/3] exec: Transform exec_update_mutex into a rw_semaphore Eric W. Biederman
2020-12-04 17:39 ` Eric W. Biederman
2020-12-03 22:42 ` [PATCH 0/3] " Linus Torvalds
2020-12-04 1:56 ` Waiman Long
2020-12-04 4:54 ` Davidlohr Bueso
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